'\" te
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.TH SIZE 9P "June 20, 2021"
.SH NAME
size, Nblock, blksize, device-nblocks, device-blksize \- device size properties
.SH DESCRIPTION
A driver can communicate size information to the system by the values
associated with following properties. Size information falls into two
categories: device size associated with a \fBdev_info_t\fR node, and minor node
size associated with a \fBddi_create_minor_node\fR(9F) \fBdev_t\fR (partition).
.sp
.LP
device size property names:
.sp
.ne 2
.na
\fB\fBdevice-nblocks\fR\fR
.ad
.RS 18n
An \fBint64_t\fR property representing device size in
\fBdevice-blksize\fR blocks.
.RE

.sp
.ne 2
.na
\fB\fBdevice-blksize\fR\fR
.ad
.RS 18n
An integer property representing the size in bytes of a block. If defined, the
value must be a power of two. If not defined, \fBDEV_BSIZE\fR is implied.
.RE

.sp
.LP
minor size property names:
.sp
.ne 2
.na
\fB\fBSize\fR\fR
.ad
.RS 11n
An \fBint64_t\fR property representing the size in bytes of a character minor
device (\fBS_IFCHR\fR \fBspec_type\fR in ddi_create_minor_node).
.RE

.sp
.ne 2
.na
\fB\fBNblocks\fR\fR
.ad
.RS 11n
An \fBint64_t\fR property representing the number blocks, in
\fBdevice-blksize\fR units, of a block minor device (\fBS_IFBLK\fR
\fBspec_type\fR in ddi_create_minor_node).
.RE

.sp
.ne 2
.na
\fB\fBblksize\fR\fR
.ad
.RS 11n
An integer property representing the size in bytes of a block. If defined, the
value must be a power of two. If not defined, \fBDEV_BSIZE\fR is implied.
.RE

.sp
.LP
A driver that implements both block and character minor device nodes should
support both "Size" and "Nblocks". Typically, the following is true: Size =
\fBNblocks\fR * \fBblksize\fR.
.sp
.LP
A driver where all ddi_create_minor_node(9F) calls for a given instance are
associated with the same physical block device should implement
"\fBdevice-nblocks\fR". If the device has a fixed block size with a value other
than \fBDEV_BSIZE\fR then "\fBdevice-blksize\fR" should be implemented.
.sp
.LP
The driver is responsible for ensuring that property values are updated when
device, media, or partition sizes change. For each represented item, if its
size is know to be zero, the property value should be zero. If its size is
unknown, the property should not be defined.
.sp
.LP
A driver may choose to implement size properties within its prop_op(9E)
implementation. This reduces system memory since no space is used to store the
properties.
.sp
.LP
The DDI property interfaces deal in signed numbers. All Size(9P) values should
be considered unsigned. It is the responsibility of the code dealing with the
property value to ensure that an unsigned interpretation occurs.
.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
.TE

.SH SEE ALSO
attach(9E), detach(9E), prop_op(9E), ddi_create_minor_node(9F),
inquiry-vendor-id(9P)
.sp
.LP
\fIWriting Device Drivers\fR
